Friedel-Crafts reactions are well known and have been summarized in monographs such as Olah, G. A. et al., Friedel-Crafts Chemistry, John Wiley & Sons, 1973, as well as other comprehensive reviews. See for example Thomas, C. A., Anhydrous Aluminum Chloride in Organic Chemistry, Reinhaldt Publishing Corp., New York, 1961.
Generally, such reactions are considered as any substitution, isomerization, elimination, cracking polymerization, or addition reaction that takes place under the catalytic effect of Lewis acid-type acidic halides (with or without co-catalysts) or proton acids.
In a specific case of a Friedel Crafts-type reaction it is known that aromatic compounds can be haloalkylated by reacting them with a hydrogen halide and an appropriate aldehyde, or with an .alpha.-haloalkyl ether or an .alpha.-haloalkyl alkyl ether, in the presence of a Lewis acid or a proton acid as a catalyst, most commonly, in the presence of zinc chloride.
The haloalkylations utilizing formaldehyde or a formaldehyde-derived ether have been successfully employed in providing fairly high yields of 1-halo-1-arylalkanes. Reasonably high yields of 1-halo-1-arylalkanes have sometimes also been obtained from haloalkylations utilizing higher aldehydes or ethers derived from them. However, it has frequently not been found possible to provide commercially acceptable yields of 1-halo-1-arylalkane from the higher aldehydes and ethers, especially when the aromatic compound has been one of the less reactive ones, such as a monoalkylaromatic hydrocarbon. There has been too much co-formation of diaryl-alkane by-product.